<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<style>
    * {
        padding: 0;
        margin: 0
    }
    .warp-flex {
        position: absolute;
        display: flex;
        width: 100%;
        height: 100%;
    }

    .warp-flex .left {
        width: 150px;
        background: blue;
    }

    .warp-flex .right {
        flex: auto;
        background: red;
    }
</style>
<body>
<div class="warp-flex">
  <div class="left"></div>
  <div class="right"></div>
</div>

</body>
</html>
